Most of the increase in May was due to a big jump in volatile commercial aircraft demand. Still, businesses also ordered more machinery, computers and household appliances.

A category of orders that’s viewed as a proxy for business investment plans — which excludes the volatile areas of transportation and defense — rose 1.5 percent. That was even stronger than solid gains in the previous two months.

This measure of business investment hadn’t increased for three straight months since the fall of 2011. The consecutive gains suggest U.S. manufacturing could improve in the second half of the year.

Manufacturing has struggled this year after helping propel the economy in the first three years after the recession ended. U.S. factories have seen less demand for exports because of weaker global growth. And businesses reduced their investment in machinery and equipment in the first quarter.

The May report showed that orders for long-lasting goods, from power generation equipment to ships and boats, rose 3.7 percent in May. Orders for nondurable goods, including paper, chemicals and oil, rose 0.7 percent.

Demand for commercial aircraft surged nearly 51 percent, after an 18.4 percent gain in April and a drop of 43.3 percent in March.

U.S. automakers on Tuesday reported healthy sales gains in June. Ford Motor Co.’s sales soared 13 percent in June compared with a year earlier. Chrysler’s sales rose 8 percent. That suggests auto production will resume a healthy pace in the coming months.

The overall gain in factory orders follows another report that shows manufacturing activity picked up in June. The Institute for Supply Management’s index of manufacturing activity rose to 50.9 from 49. Any reading above 50 indicates expansion.

The ISM index showed that new orders and production both jumped. But a gauge of employment fell sharply, suggesting factories cut jobs for the fourth straight month.

The U.S. economy expanded at only a 1.8 percent annual rate in the first three months of the year, the Commerce Department said last week. That was much slower than its previous estimate of a 2.4 percent rate.

The main reason for the downgrade was consumers spent less on services than initially thought. Spending on long-lasting factory goods, such as cars and appliances, was stronger.

Economists expect growth remained tepid in the April-June quarter. Most estimates range between a rate of 1.5 percent and 2 percent.